1. Field of the Invention
The present invention is in the field of digital deemphasis circuits for volume-compressed, amplitude-normalized audio signals which are digitized in the two's complement binary system, and, in particular, in the field of digital deemphasis circuits which can be implemented in the audio sections of television receivers designed to receive the Electronics Industries Association (EIA) Broadcast Television Systems Committee (BTSC) multichannel television standard
2. Description of the Related Art
The EIA BTSC is a relatively new standard for transmission of stereo information with the simultaneous opportunity for broadcasting a separate second audio program. The system of this standard is described in detail, for example, in Leslie B. Tyler, et al., "A COMPANDING SYSTEM FOR MULTICHANNEL TV SOUND," IEEE Transactions on Consumer Electronics, November 1984, pp. 633-640. In that article, the individual subcircuits in the described system are presented as analog-signal-processing circuits. Of particular interest in connection with the present invention are FIGS. 5 and 15 and the text of the description on pages 636.639.
It is desirable to use digital circuits in place of analog circuits in modern television receivers. The prior-art analog circuits described in the Tyler, et al., article, like many other analog circuits, cannot be readily converted to corresponding digital circuits for processing signals digitized by an analog-to-digital converter because, in the present case for example, such a direct replacement of analog circuits by corresponding digital circuits would lead to a feedback control loop without delay, which cannot be implemented digitally.